There is a related art image forming apparatuses that include a photosensitive drum carrying a toner image and rotating, and a driving coupling for transferring the driving force to the photosensitive drum. According to this related art image forming apparatus, the driving coupling is capable of advancing and retreating in an axis direction, so it is attached to and detached from an aperture formed on the end of the photosensitive drum, and when the driving coupling is attached to the photosensitive drum, the driving coupling and the photosensitive drum are engaged with each other in the circumferential direction and rotate integrally.